Having it be an array encourages multiple uses for the same key. I have stated many times that encouraging people to do that is not a good idea, and making it easy makes people think it is a good idea.
You can use the single value field and have multiple entries with different key containing the same or different keys to do the same thing. On the practical side "use_details" is better than creating crazy dot separated como uses. John B. On Dec 24, 2013, at 8:26 PM, Mike Jones <[email protected]> wrote: > Hi all, > > Having reflected upon discussions among WebCrypto and JOSE participants about > JWK usage by WebCrypto over the holidays, I’d like to propose the two JOSE > spec actions to more closely coordinate with WebCrypto: > > 1. Change the JWA registry field name from “Implementation Requirements” to > “JOSE Implementation Requirements” in the JSON Web Signature and Encryption > Algorithms Registry > (http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-18#section-7.1). > This will make it clearer that the Implementation Requirements apply only > to JWS and JWE implementations – and not other uses of JWK (such as > WebCrypto). This changes only non-normative text and is non-breaking. > > 2. Define the new JWK field “use_details” for recording intended > fine-grained key usage information. This would enable WebCrypto KeyUsage > (https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#key-interface) > values to be used directly with JWK. The proposed definition is: > > 3.3. "use_details" (Key Use Details) Parameter > The "use_details" (key use details) member identifies fine-grained > details the intended use of the key. Its value is an array of > key use details values. Values defined by this specification are: > > o "sign" (compute signature or MAC) > o "verify" (verify signature or MAC) > o "encrypt" (encrypt content) > o "decrypt" (decrypt content and verify decryption, if applicable) > o "wrap" (encrypt key) > o "unwrap" (decrypt key and verify decryption, if applicable) > o "deriveKey" (derive key) > o "deriveBits" (derive bits not to be used as a key) > > Other values MAY be used. Key Use Details values can be registered > in the IANA JSON Web Key Use Details registry defined in Section 7.3. > The use details values are case-sensitive strings. > Duplicate use details values MUST NOT be present in the array. > Use of the "use_details" member is OPTIONAL, unless the application > requires use this member to record fine-grained key usage details. > (Note that the "use_details" values intentionally match the "KeyUsage" > values defined in the WebCrypto [WebCrypto] specification.) > > If both "use" and "use_details" JWK members are present, the usages > specified by them MUST be consistent. In particular, the "use" value > "sig" corresponds to "sign" and/or "verify". The "use" value > "enc" corresponds to all other values defined above. > If "use_details" values corresponding to both "sig" and "enc" > "use" values are present, the "use" member SHOULD NOT be present, > and if present, its value MUST NOT be either "sig" or "enc". > > This is a non-breaking change – allowing simple applications that want to > distinguish between signing and encryption operations to continue doing so as > they do today, while also providing a multi-valued key usage details field to > be used by applications that want to record fine-grained distinctions among > potential key usages, including distinguishing between producer and consumer > operations. > > As I see it, while having two related key usage representations isn’t ideal, > it’s far better than having WebCrypto overload “use” with multi-valued values > encoded in strings, such as “signOnly,verifyOnly”, which I believe is their > current plan of record. > > Comments? > > -- Mike > > P.S. This proposal was already discussed on the WebCrypto list in the thread > http://lists.w3.org/Archives/Public/public-webcrypto/2013Dec/0052.html and no > objections were raised there that I’m aware of. > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose
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